In an exposure apparatus which uses, as an exposure light, for example an ultraviolet light in the far-ultraviolet region to vacuum ultraviolet region and which is used in a lithography process for producing electronic devices (micro devices) such as semiconductor devices, etc., shorter wavelength of the exposure light, optimized illumination condition, and the liquid immersion method for further increasing the numerical aperture of a projection optical system have been adapted, for the purpose of enhancing the resolution, In the recent years, the Pitch-Splitting Process and the Spacer Double Patterning Process (Spacer Transfer Process or Sidewall Transfer Process) have been proposed as a method for forming a periodic circuit pattern having a pitch finer (more minute) than the resolution limit of the exposure apparatus (see, for example, Andrew J. Hazelton et al., “Double-patterning requirements for optical lithography and prospects for optical extension without double patterning,” J. Micro/Nanolith, HEMS MOEMS, (U.S.A.), Vol.8(1), 011003, January-March (2009)).
The Pitch-Splitting Process is generally classified to the Double Exposure process and the LELE process (Litho-Etch-Litho-Etch process) or the LPLE process (Litho-Process-Litho-Etch process). In the Double Exposure process, a non-linear resist is exposed with images of first and second mask patterns, each of which has a pitch twice the pitch of a device pattern which is to be finally produced, in a state that the phases of the images are shifted from each other, and then etching, etc., is performed (see, for example, H. Ohki et al. “Experimental study on non-linear multiple exposure method”, Proc. SPIE (U.S.A.), 3051, p.85-93 (1997)). In the LELE process or the LPLE process, a process such as the etching, etc. is performed between the exposure with the image of first mask pattern and the exposure with the image of the second mask pattern.
In the Spacer Double Patterning Process (Spacer Transfer Process or Sidewall Transfer Process), for example, exposure with an image of a mask pattern having a pitch twice the pitch of a device pattern and a development of the image, etc., are performed to form a plurality of line patterns having a line width that ¼ of the pitch; a spacer is allowed to be deposited in space portions (side wall portions) located at both sides in each of the line patterns, and then, for example, each of the line patterns is removed. By doing so, a patter. having a pitch that is ½ of the pitch the image of the mask pattern can be obtained (see, for example, N. Jung et al., “Patterning with amorphous carbon spacer for expanding the resolution limit of current lithography tool”, Proc. SPIE (U.S.A.), 6520, 652010 (2007)).